Process for obtaining an alpha-lactalbumin enriched product from whey and uses thereof

ABSTRACT

A process of obtaining an α-lactalbumin enriched product from whey of various origins is disclosed. A first ultrafiltration is carried out on unpasteurized raw whey with membranes having cut-off greater that 5,000 (e.g. 50,000) at a pH between 6:3 and 7 (e.g. 6.6) and a temperature between 30° and 60° C. thereby retaining whey proteins. The ultrafiltrate then undergoes a second ultrafiltration with a membrane capable of retaining α-lactalbumin (cut-off about 1,200 and 2,000) which is preferably diafiltration. Depending on whether starting whey is acid whey or sweet whey the resulting product may contain practically no CMP or some (e.g. 25%). The resulting product is useful as a mother&#39;s milk substitute, pharmaceutical, intensive care or therapeutic food, or tryptophan enriched nutrient.

This application is a continuation of application Ser. No. 647,069,filed Sept. 4, 1984, now abandoned, which is a continuation ofapplication Ser. No. 338,136, filed Jan. 8, 1982, now issued as a U.S.Pat. No. 4,485,040, which is a continuation of application Ser. No.162,641, filed on June 24, 1980, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the field of treatment of whey with a view toextracting valuable products.

2. Description of the Prior Art

Whey is a well-known by-product of the cheese-making industry. Thecomposition of whey is approximately that of skim milk without itscasein. In general, two main types of whey may be distinguished, sweetwheys, or cheese plant wheys, and acid wheys or casein plant wheys.

The addition of rennet to milk causes syneresis which results in a wheycalled rennet whey. If the renneting occurs at a pH of milk or at aslightly lower pH for example after slight maturation by lactic yeasts,but above a range of about 5.8 to 6, the whey is designated sweet whey.Moreover, the acidification of milk either by adding a mineral acid orby producing lactic acid (seeding milk with lactic ferments) at a pHnear the isoelectric point of the caseins, causes the flocculation orcoagulation thereof. After separation of the curd, an acid whey isobtained.

Whey is therefore defined with respect to the nature of the coagulationof the milk. In the cheese industry most of the wheys are in fact mixedwheys where one of the coagulation processes prevails over another. Thesweet wheys come from the manufacture of cheeses called (cooked oruncooked) pressed curd (Emmental, Gruyere, Cheddar, Cantal, Saint-Paulinetc . . . ). Acid wheys are chiefly the by-products of the manufactureof fresh curds and casesin plants. Intermediate varieties are also foundwhich are the by-products of the fabrication of most soft curds andmarbled curds (blue cheese). Thus, the composition of wheys is subjectto wide variations which mainly depend upon the original milk and thecheese-making procedures used.

Wheys have interesting constituents,, notably the nitrogenous fractionwhich essentially comprises soluble milk proteins which have an elevatedbiological value, greater than 90%. Reference can be made to the articleby E. FORSUM and L. HAMBRAEUS, Nutritional and Biological Studies ofWhey Products, J. of Dairy Sc., 60 (3), 370-377, 1977. Heretofore thethree traditional destinations of wheys were spreading on fields,dumping in waterways and feeding animals. But the interest is now in newtechnologies involving, for example, ultrafiltration which permitsseparation, concentration and purification of the whey componentsselectively and modification of their physical-chemical properties whilemaintaining and even improving their nutritional quality. At the presenttime more and more research is directed to techniques of treating wheypermitting the preparation of novel and varied products capable offinding uses as foodstuffs. Workers in the field have a particularinterest in the proteins contained in the whey in order to obtain variedfood products capable of satisfying specific requirements.

Numerous documents of the prior art illustrate treatments of whey byultrafiltration. In the cheese-making field it has already been proposedto ultrafiltrate the whey to produce a "retentate" (which is concentrateheld back by the ultrafiltration membrane) containing soluble proteins,the retentate then being reintroduced into the cheese in the process offabrication. Yet there are whey ultrafiltration processes which permitdifferential or selective separation of various components. The processaccording to the present invention falls into the latter category.

An object of the invention is a process for obtaining from whey byultrafiltration, a α-lactalbumin enriched product. Although in relativeterms the proteins represent a small part of the solids content of thewhey (less than 12%) they are the main attraction for increasing thevalue of this by-product. The proteinaceous fraction essentiallycomprising soluble milk proteins: β-lactoglobulin, α-lactalbumin, serumalbumin and immunoglobulins, is interesting by reason of its nutritionalvalue and its fonctional properties.

Numerous works exist on the characterization of the soluble proteins inwhey. As regards β-lactoglobulin reference may be made to the work by G.Braunitzer, R. Chen, B. Shrank, A Stangl, Automatic Sequence Analysis ofProtein (β-lactoglobulin AB), Hoppe Seyier's Z. Physiol. Chem. 353 (5),832-834, 1972. Briefly, it may be observed that the β-lactoglobulin, byreason of the presence of a free SH group, has the tendency topolymerize and to exist in the form of a monomer-dimer-octamerequilibrium. The dimer from prevails in general in ultrafiltrationconditions and at low temperature at pHs closer to the isolectric point(pH about 5 favors octamerization). At a pH greater than 7.5 the balancetips in favor of the monomer form. The conformation of theβ-lactoglobulin is relatively stable below pH 7. H. A. McKenzie, MilkProteins, vols 1 and 2, Academic Press, New York, 1970, made a study ofthe forms and characteristics of β-lactoglobulin. The effect of the pHon the conformation of this protein has been confirmed (see, forexample, E. Mihalyi, Application of Proteolytic Enzyme to ProteinStructure, 1972).

As for α-lactalbumin its sequence is generally known, see K. Brew, F. J.Castellino, T. C. Vanamam, R. L. Hill. The Complete Amino Acid Sequenceof Bovine α-Lactalbumin, J. Biol. Chem. 245 (17), 4570-4582, 1973.Contrary to β-lactoglobulin it does not have a free SH group. The workof D. N. Lee and R. L. Merson "Prefiltration of Cottage Cheese Whey toReduce Fouling of Ultrafiltration Membranes", J. Food Sc. 41: 403-410,1976, has demonstrated that the form of the α-lactalbumin molecules mayvary in accordance with the pH. At acid pHs the molecules have thetendency to associate in dimer or trimer form. At pHs greater than 8 apolymerization of the protein is also found.

Like β-lactoglobulin, serum albumin possess a free SH group and existsin monomer and dimer forms.

It is also know that the coagulation of milk is obtained byacidification or proteolysis of the K casein. This enzymatic hydrolysiswith rennet frees from the whey a phosphoglycopeptide calledcaseinomacropeptide (CMP). The quantity of CMP in wheys varies accordingto the nature and the coagulation time, it may attain at the utmost 1g/l in sweet whey.

Numerous other soluble proteins exist in milk and wheys. Their presencein smaller quantities than the preceeding makes them less important bytheir contribution ot the physical-chemistry of the protein concentrateof whey than their biological role.

The oldest technique for extracting proteins from whey consists ofmaking them insoluble by a denaturing heat treatment at a pH close totheir isoelectric point. This process, which is widely used was recentlyreviewed by B. P. Robinson, J. L. Short, K. R. Marshall, TraditionalLactalbumin Manufacture, Properties and Uses, N. Z. J. Dairy Sc. andTechn., 11 (2), 114-126, 1976. The drawback of this technique isobviously its denaturing aspect. Other laboratory processes haveessentially tried to remedy this drawback. It has, for example, beenproposed to carry out an adsorption of proteins in an ion exchanger (J.B. Ward, Separation Processes in the Biological Industry, ProcessBiochemistry, 11 (7), 1976. The ion exchange technique entailsautomation and continuous operation difficulties,, great investments(amounts of resin eluent, concentration of eluates). The obtention ofpurified products is not always an advantage.

Other processes call upon chemical extractions and do not give totalsatisfaction from the nutritional standpoint. Chromatographic ionexchange processes have also been suggested (see B. Mirabel, Nouveauprocede d'Extraction des Proteines du Lactoserum, Ann. de la Nutritionet de l'Alimentation, 34 (2-3), 243-253, 1978. Filtration through a gelhas also been used, but essentially in the laboratory. R ference may behad, for example, to the work of L. O. Lindquist and K. W. Williams,Aspects of Whey Processing by Gel Filtration, Dairy Industries, 38 (10),459-464, 1973, and the work of E. Forsum, L. Hambraeus, and I. H.Soddiqt, Large Scale Fractionation of Whey Protein Concentrates J. ofDairy Sc., 57 (6), 659-664, 1974. The processing by gel filtration has anumber of drawbacks. It requires, notably, a preconcentration ofproteins which must not be denatured at the risk of altering theresolution between the different fractions. These fractions must then beconcentrated and dried. The inferior mechanical properties of gels andthe clogging capacity of whey concentrates by reason of the presence oflipoprotein complexes have made this procedure very limided.

Ultrafiltration through a membrane, given the progress made with regardto both apparatus and their performance, has become widely used in thedairy industry both for treating milk and whey (see, for example, thework of Mocquot et al, Preparation de Formage a Partir de "Prefromageliquide" obtenu par Ultrafiltration du Lait, Le Lait, 51 (508) 495-533,1971.

During the filtering of whey through an ultrafiltration membrane, thewater, soluble mineral salts and water-soluble vitamins pass through themembrane. The product which passes through the membrane is known as theultrafiltrate or permeate. On the other hand the proteins and associatedconstituents (calcium, phosphorus), fat globules and lipophilic elementsare held back or retained and are concentrated as the aqueous phase iseliminated. These constituents are known as the "retentate" or proteinconcentrate. The protein concentrates obtained by ultrafiltration may bedefined either by the concentration factor or by the degree of purity ofthe proteins. The obtention of high purity concentrates necessitates theapplication of ultrafiltration followed or accompanied by diafiltrationwhich consists in washing the protein concentrates. During diafiltrationthe liquid to be ultrafiltrated is brought into contact with themembrane at the same time as the solution, e.g., an aqueous solution.Numerous studies have been made on the composition of the wheyultrafiltrate. [See, for example, Hargrove et al. Production andProperties of Deproteinized Whey Powders, J. of Dairy Sc., 59 (1), 5-33,1976, Hiddink et al Ultrafiltration of Condensed Whey, Zuivelzicht 68(48-51), 1064-1066, 1126-1127, 1978; L. Kivieniemi, Microbial GrowthDuring the Ultrafiltration of Sweet Whey and Skim Milk, Kemia-Kemi, 12,791-795, 1974]. The composition of retentates or protein concentrateshas also been determined. (See, for example B. S. Horton, R. L.Goldsmith and R. R. Zall, Membrane Processing of Cheese Whey ReachesCommercial Scale, Food Technol. 26 (30), 1972.

The actual conditions of ultrafiltration are such that it does notproceed according to ideal hypotheses. For instance, the ultrafiltrationretentate has a relatively great residual content of fat as well as ofmineral elements. Further, current ultrafiltration membranes havevariable pore diameters. Their cut-off capacity is therefore notabsolutely accurate and does not correspond to an ideal isoporousmembrane. Furthermore the membrane is not inert. The temperature,pressure and pH may modify its physical properties and thereby thediameter of the pores and the hydration of the membrane may vary.Depending on the chemical nature of the membrane, ionic or hydrophobicinteractions may develop between with the proteins and/or the minerals.In addition to these types of bonding one must add the possible physicalcapture of molecules in the pores of the membrane. All these phenomenamodify the permeability of the membrane with respect to theultrafilterable elements and water. Finally, it is necessary tounderscore the importance of the formation on the ultrafiltrationmembrane of a polarization layer also known as a dynamic membrane whichmainly comprises proteins. Without mastering this phenomenon anyamelioration as regards selectivity of the membranes is largelycompromised: see J. Murkes, Quelques Opinions sur les ApplicationsIndustrielles de la Technologie des Membranes, Journees Europeennes dela Filtration, Paris, Oct. 21, 1978. In other words the capacity of amembrane to satisfy a given function must not be appreciated ideally:the membrane must compulsorily be tested in operating conditions becauseit is impossible to disregard the polarization layer which forms in thecourse of ultrafiltration and modifies the transfer of solutes acrossthe membrane, thereby lowering the performance of the apparatus, inparticular, the permeation rate. Qualitative changes in the retentateand permeate may also be observed. This polarization layer serves as asecond membrane and the total permeability of the membrane in the courseof operation will depend on its thickness and also the nature of itscomponents.

As regards the ultrafiltration of whey, reference may be had to the workby D. N. Lee and R. L. Merson, Prefiltration of Cottage Cheese Whey toReduce Fouling of Ultrafiltration Membranes, J. of Food Sc. 41, 403-410,1976. These authors determined a number of conditions which permit thethickness and density of the polarization layer to be minimized in orderto improve the permeability of the membrane. They also noted theinfluence of pH which acts on the solubility of the proteins. It istherefore recommended to adjust the pH to take into account the originof the whey. See also J. F. Hayes, J. A. Dunkerley, L. L. Muller and A.T. Griffin, Studies on Whey Processing by Ultrafiltration II ImprovingPermeation Rates by Preventing Fouling, The Australian J. of Dairy Tech.37 (3), 132-140, 1974. The authors teach the preheating of whey, forexample, to 80° C. for 15 seconds, which will have the effect ofimproving the performance of the apparatus. Generally speaking it isalso known to pretreat the wheys, i.e., heat treatment, notably bypasteurization to prevent bacterial contamination. Indeed it is knownthat whey contains 10 to 20% of the bacteria of milk manufactured.Pasteurization has therefore often been recommended to preserve thehealthy quality of the whey.

The aforesaid articles by Lee and Merson (1976) and Hayes to whichreference may be had if necessary, show that the conditions forultrafiltrating wheys are of great practical importance.

Operations called diafiltration are also known, these operations consistof adding water to the retentate and simultaneously or subsequentlyeliminating an equivalent amount of permeate. The effect ofdiafiltration is to reduce the filterable elements from the retentate.It may be a batch process (dilutions followed by successiveconcentrations) or a continuous (water is added at the same rate as thepermeate is eliminated). The diafiltration permits, in general, proteinconcentrates of enchanced purity to be obtained.

By way of example of references illustrating the prior art in the fieldof ultrafiltration the following may be cited: French patents Nos.71.04.839 (printed publication No. 2.125.137) and 74.24.441 (printedpublication No. 2.239.208), Chemical Abstracts, Vol. 81, No. 3, July 22,1974, p. 218, Abstract No. 11969, referring to an article in Sci.Tecnol. Alimenti 1973, 3 (4) 209-215 by C. Pompei et al.

The French Pat. No. 71,04,839 relates to the delactosation of milk andproposes a process for producing a milk containing all the constituentsof natural milks with the exception of lactose; such a product is usefulfor feeding diabetics. The disclosed process deals with the milk as astarting material and not whey, and it involves in addition at least onereverse osmosis step. Typically, the process according to French Pat.No. 71,04,839 consists in ultrafiltering milk, recovering theultrafiltrate, subjecting the ultrafiltrate to reverse osmosis with aview to eliminating the lactose contained therein whereupon the effluentof the reverse osmosis is mixed with the ultrafiltration retentate toprovide a reconstituted milk without lactose.

French Pat. No. 74,24,441 proposes to treat milk or whey byultrafiltration by diluting the retentate with an aqueous solution inorder to produce human milks in particular. After ultrafiltration of thewhey a product which may be spray dried is obtained which after mixingwith sodium caseinate results in an additive which is may be added tothe milk to correct or modify the casein/soluble proteins ratio. Such aprocess therefore involves all the soluble proteins of whey. The articleby C. Pompei et al. cited above also proposes treating whey byultrafiltration to yield a protein concentrate which may be sprayed.Such a process enables all the whey proteins to be isolated but does notteach the fractionation thereof.

Observation of the prior art has shown that the retention of solublewhey proteins by the ultrafiltration membrane as classically used at thepresent time in industry is not complete. The retention also differsdepending on the nature of the proteins.

Thus α-lactalbumin may pass freely through currently used membranesowing to its small molecular weight (14,000-15,000), its compactglobular configuration and its inability to polymerize in a undenaturedstate by reason of the absence of free SH groups. Yet, in actualoperating conditions of ultrafiltration a partial retention ofα-lactalbumin is found which is surely due to the presence of thepolarization layer of dynamic membrane on the actual membrane. As forβ-lactoglobulin which is also found to be partly retained, it passes,across the membrane in its monomer form. pH conditions therefore take onconsiderable importance.

SUMMARY OF THE INVENTION

The invention takes advantage of these observations of the prior art andprovides a process which permits, owing to the utilization of atechnique of ultrafiltration of whey under industrial conditions, aproduct very enriched in α-lactalbumin is obtained to the detriment ofother proteins soluble in whey.

To this end the invention provides a selective or differential treatmentof whey which permits, after successive ultrafiltration, selecting theα-lactalbumin enriched fraction. Each of the ultrafiltration isconducted under predetermined conditions and with predeterminedmembranes.

Another object of the invention is a product obtained directly by theprocess, namely an α-lactalbumin enriched fraction.

Another aspect of the invention is the application of this product, inparticular in the food and medicine field, as a dairy product substituteor complement, notably by way of a food fulfilling specific nutritionalrequirements, for example, to give the qualities of mother's milk, forintensive-care by the enteral tract as well as for human or animaltherapeutic nutrition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates the first and second ultrafiltrationsteps of the present process.

FIG. 2 illustrates the analysis and characterization of the finalretentate evidenced in the presence of a mixture α-lactalbumin,β-lactoglobulin and glycosyl or non-glycosyl CMP.

FIG. 3 evidences the analysis of an ultra-filtration product evidencedin a first peak corresponding to α-lactalbumin, and a second peakcorresponding to β-lactoglobulin.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the invention there is provided a process for obtaining anα-lactalbumin enriched product by ultrafiltering whey, the processcomprising the steps of effecting a first ultrafiltration of the wheywith known membranes having a cut-off generally greater than 5,000,intended to permit the retention of whey proteins called solubleproteins, the first ultrafiltration being carried out on raw whey at apH equal to at least 6.3 and preferably of the order of 6.6, subjectingthe ultrafiltrate from the first ultrafiltration to a secondultrafiltration by bringing the first ultrafiltrate into contact with amembrane capable of retaining α-lactalbumin, preferably having a cut-offless than 5,000 and advantageously between about 1,500 and 2,000, andrecovering the retentate of the second ultrafiltration which constitutesthe α-lactalbumin enriched product sought.

First of all it is important to define the raw material used in theprocess according to the invention. The intrinsic nature of the whey maybe of any kind whatever insofar as the process is equally applicable tosweet whey from cheese-making and acid wheys. Still the resultingproducts from each of these starting materials are different. When sweetwhey is the starting material an α-lactalbumin enriched product isobtained having a small proportion of β-lactoglobulin and some CMP. Onthe other hand, if acid whey is the starting material the α-lactalbuminenriched product has practically no CMP. Thus, depending on the originof the whey the product resulting from the process may contain more orless or no caseinomacropeptide. It is appropriate to note that CMPexists in two forms:

glycosyl form: composed of two different dractions depending on thenature and amount of branched sugars (galactosamine galactose,N-acetyl-neuraminic acid); and

nonglycosyl form.

CMP also contains one or two phosphoserines, no aromatic amino acid(tryptophan, phenylalanine, tyrosine) and is rich in threonine, prolineand serine.

It is appropriate to use a whey, regardless of its origin, which hasundergone no previous heat treatment of the type which is customarilycarried for pasteurization. The objective of this operation is toeliminate possible bacterial contaminants. In the context of the processaccording to the invention as soon as the whey is collected it issubjected to a conventional skimming operation which is intended toremove the fat which is still present in the raw whey, whereupon it mayundergo the first ultrafiltration. It may also be kept for a suitableperiod of time at low temperature, for example, of the order of 0° to 4°C., while, however, preventing the crystallization of lactose. Ofcourse, during the first ultrafiltration the whey may be heated toincrease the yield. For example, the suitable temperature may be of theorder of 30° to 60°, preferably of the order of 45° C. Butultrafiltration may also be conducted at ambient temperature. It isabove all important that before or during ultrafiltration the whey isnot heated to as high a temperature as involved in conventionalpasteurization.

Another important consideration concerning the performance of the firstultrafiltration is with regard to the pH of the whey. According to theinvention the pH of the raw whey should be adjusted to a value slightlyless than 7, nevertheless at least equal to 6.3 and preferably of theorder of 6.6. Taking into account the properties of typical wheys thisadjustement is effected conveniently by adding basic reagents. Inprinciple, any base may be used, such a sodium hydroxide, potassiumhydroxide, sodium carbonate, potassium carbonate, calcium hydroxide,ammonium hydroxide and other similar basic compounds.

Potassium hydroxide is preferred on account of the ultimate use of theproducts as foodstuffs.

Moreover the first ultrafiltration is carried out in perfectly knownconditions. Any currently available equipment may be used, for example,plate, bundle or tube ultrafiltration modules. The semipermeablemembranes used are those already known for retaining or concentratingsoluble proteins. In general these membranes have a cut-off greater than5,000 for example, of the order of 50,000. The nature of the membrane isof no importance. It may be an inorganic or organic membrane. By way ofexample of organic membranes any porous substrate satisfying the abovedefinition may be used. All these concepts are well known to thoseskilled in the art of ultrafiltration of milk or whey and therefore neednot to be explained further.

In the operating conditions of the first ultrafiltration the membranebehaves like a membrane not designed to concentrate or retain theα-lactalbumin and therefore allows it to pass across the same. At theconclusion of ultrafiltration an α-lactalbumin enriched solution istherefore obtained. Indeed, in such a solution theβ-lactoglobulin/α-lactalbumin ratio is inversed as compared to thestarting whey. In addition the ultrafiltrate comprises no proteinshaving a molecular weight greater than about 20,000.

As mentioned above, the first ultrafiltration is conducted in a knownmanner. If necessary it is possible to have recourse to a preliminarytest to determine the exact membrane which suits this step, taking intoaccount its dynamic behavior.

In accordance with the invention the ultra-filtrate separated during thefirst ultrafiltration is then subjected to a second ultrafiltrationduring which it is used as a membrane capable of holding back orconcentrating the α-lactalbumin. As a general rule such a membrane has acut-off of less than 5,000 and preferably between about 1,500 and 2,000.The chemical and/or physical nature of the membrane matters little aslong as it satisfies the α-lactalbumin retaining condition in theoperating conditions of the process according to the invention. In thesame way the first ultrafiltration any available ultrafiltrationequipment may be employed. Usually it is advantageous to carry out adiafiltration rather than an ultrafiltration, i.e., conduct theultrafiltration by adding continuously or discontinuously to theultrafiltrate from the first ultrafiltration an aqueous solution or purewater or an aqueous solution containing mineral salts upstream of themembrane relative to the direction of permeation in the secondultrafiltration.

The second ultrafiltration produces an ultrafiltrate consisting oflactose juice and a retentate or concentrate comprising the soughα-lactalbumin enriched solution. The invention is illustrated by FIG. 1of the accompanying drawing which schematically illustrates the steps ofthe process.

The products obtained according to the invention are useful as afoodstuff, in particular a human foodstuff. It is known that human milkcontains approximately 40% casein and 60% soluble proteins, butβ-lactoglobulin is not one of them. To reconstitute milk which comes asclose as possible to human milk it is therefore appropriate that themilk product should no contain any β-lactoglobulin while fulfilling inother respects the composition of mother's milk. The products producedaccording to the invention therefore satisfy such a need and thereforeare suitable for what is called "motherization" of the milk. Moreover,it may be useful to have available an α-lactalbumin enriched product forparticular dietary requirements, α-lactalbumin being a protein which hasthe pecularity of being very rich in tryptophan. In such foodstuffapplications the product produced according to the invention may be usedas a complement or a substitute for human foods or animal feeds.

The products according to the invention may have other uses by reason oftheir particular properties. These products are rich in tryptophan whichmay be used as food for dietary or therapeutic purposes.

In particular in these products the ratio of tryptophan to so-calledneutral amino acids (tyrosine+phenylalanine+leucine+isoleucine+valine)is high, in particular, greater than or equal to 0.06. Thetyrosine/tryptophan ratio is correspondingly low, in particular, lessthan 2.5 and may reach values in the vicinity of 1.

The products according to the invention are therefore usable as dieteticproducts for man or animals. It may also be used as intensive-careproducts or foodstuffs for patients requiring a specific protein diet.These products satisfy nutritional needs in case of, for example,mucoviscidosis or cystic fibrosis of the pancreas, kidney disorders orfor patients having an infection or inflammation of the intestinal wallas well as in the case of considerable tissue distruction after severetraumas or burns.

The products of the invention may also have use in therapeutic nutritionof humans and animals. Earlier work (see in particular the articles byR. J. Wurtmann and J. D. Fernstrom in Nutrition Review, 7 (32), 193-200July 1964, and in The American Journal of Clinical Nutrition, (28),638-647, June 1975) have demonstrated the possibilities of increasingthe tryptophan content available inside the brain cell by varying theamounts and equilibrium of amino acids of ingesta may be of interestfrom the neuropharmacological strandpoint. The tryptophan is a serotoninprecursor. Likewise a similar action of the intake of tyrosine andphenylalanine and their equilibrium with respect to other amino acidsare capable of affecting the amount of dopamine and noradrenaline. Ananorexigenic effect may be observed by increasing the tryptophan contentalone without diminishing the biological value of the protein mixturesby a balance phenomenon. The same effect may be amplified by alwaysstaying within the identical biological value framework while loweringthe amount of phenylalanine and tyrosine.

The products of the invention may therefore be used by man or animalswith a view to therapeutic nutrition notably for treating obesity bytaking advantage of the anorexigenic effect or to regulate eatingbehavior. Further, the products of the invention may be used to improvepharmacological efficacy of pharmaceuticals permitting man or animals toincrease the production of neurotransmitter amines, namely, serotin, onthe one hand, and dopamine and noradrenaline, on the other. By way ofexample tranquilizers may be increased in the course of transportinganimals which have received a product according to the invention.

Taking account of the physical form of the new products (soluble powderin an aqueous medium) the form in which it is presented does not giverise to any difficulties. The novel products may be administered as suchby the enteral tract or, for example, mixed with a common foodstuff.

Doses of 0.1 to 2 g/kg per day are suitable.

The invention will now be illustrated without in any way being limitedthereby, with reference to the examples hereinbelow.

EXAMPLES EXAMPLE 1

In this example a rennet type whey is used as the starting material.This whey was obtained by coagulation of skim milk, heat treated (72° C.for 15 seconds), not cooled, with 30 ml of Boll rennet (10⁻⁴) thenfiltered.

After storing it for 18 hours at 4° C. the whey was ultrafiltered at 45°C. in a DC 10 ultrafiltration module with an XM 50 membrane (1.4 sq m)sold by Romicon. XM 50 membranes are indicated by the manufacturer ashaving a cut-off in the vicinity of 50,000. The DC 10 ultrafiltrationmodule uses membrane of the hollow fiber type, bunched in tubularbundles. The ultrafiltration permeate was recovered and its compositionwas followed with time. The results are tabulated in table 1 below:

                  TABLE 1                                                         ______________________________________                                                NPN g/l  NT g/l  NPN/N.sub.T                                                                            NT/ES                                       ______________________________________                                        UF.sub.o  0.237      2.1     0.72   3.1%                                      UF.sub.1H 0.250      2.6     0.62                                             UF.sub.2H 0.262      3.0     0.56                                             UF.sub.3H 0.255      2.9     0.57                                             UF.sub.4H30MIN                                                                          0.259      2.5     0.47                                             UF.sub.5H50MIN                                                                          0.243      3.9     0.40   6.1%                                      ______________________________________                                    

The ultrafiltrate obtained from the first ultrafiltration through the XM50 membrane was collected and again ultrafiltrated through am AM₂membrane at 15° C. also by using a DC 10 ultrafiltration module byRomicon. The surface area of the membrane was also equal to 1.4 sq.m.and the membrane was of the hollow fiber type. The AM₂ membranecomprises a cut-off of the order of 2,000. The change of the compositionof the retentate in the course of this second ultrafiltration istabulated in table 2 which follows.

                  TABLE 2                                                         ______________________________________                                                Retentate          Permeate                                                   Prot.                                                                              NPN.sub.6.38  N.sub.T                                                                             ES.sub.g/l                                   ______________________________________                                        Ao        3.1    1.5           1.6 57.0                                       A.sub.22  4.5    1.7           1.6                                            A.sub.42  5.3    1.7           1.7                                            A.sub.62  7.1    1.8           1.7                                            A.sub.82  8.0    1.9           1.7 60.3                                       A.sub.F   12.4   2.1           1.7 60,7                                       ______________________________________                                    

In order to analyze and therefore charactirize the final retentate, itwas filtered through a G 75 gel in a phosphate buffer medium (pH 7.0) ona column (2 m×0.02) at a flow rate of 15 ml/h. The metering was effectedon an eluent of neuraminic acid, the optical density measurement at 230nm and the measuring of the ninhydrin at 750 nm. The results areillustrate by FIG. 2. The main peaks may be distinguished therein.

1. DO₂₃₀ low/NH₂ 570 NaNa high

2. DO₂₈₀ low/NH₂ 570

3. DO₂₈₀ high/NH₂ 570

The analysis of the entire sample by electrophoresis and the differentpeaks is proof that the retentate comprises a mixture of α-lactalbumin,β-lactoglobulin and glycosyl or nonglycosyl CMP.

In order to determine the respective amounts, the soluble nitrogen wasmetered in different strengths of trichloroacetic acid [see K. Fox etal., Separation of β-lactoglobulin from Other Milk Serum Proteins byTrichloroacetic acid, Journal of Dairy Science, Vol. 50., No 9,pp1363-1367, 1967]. It is then shown that:

at 2% about 75% of the β-lactoglobulin, all the CMP and a residue ofα-lactalbumin-soluble nitrogen (peptides+free amino acids) remainsoluble:

at 4% about 50% of the β-lactoglobulin, all the CMP and anα-lactalbumin-soluble-soluble-N (peptides+free amino acids) remainsoluble;

at 6% all the CMP--soluble N remains soluble; and

at 12% all the glycosyl CMP-soluble N remains soluble;

    ______________________________________                                        Results:                                                                      2%       4%            6%     12%                                             ______________________________________                                        ppm of N                                                                      262      224           183    119                                             ______________________________________                                    

The product corresponds to approximately the following composition byweight:

    ______________________________________                                               lactalbumin                                                                            47%                                                                  lactoglobulin                                                                          20%                                                                  CMP      25%                                                                  soluble   8%                                                           ______________________________________                                    

From the above figures and the amino acid composition of each of theconstituents the theoretical aminogram was determined which was comparedwith the real aminogram.

We found a coefficient of correlation of 0.96. By disregarding theglutamic acid and the proline which are known to be the chief aminoacids of the soluble phase of the U.F. permeate (Hargrove et al., J.Dairy Science, 59, 25-33, 1976) the coefficient becomes 0.986 which isin good correlation with actual values.

It is interesting to note owing the presence of α-lactalbumin, therichness of tryptophan (nearly twice as great as the normal percentageof the initial concentrate).

    ______________________________________                                                  Theoretical model                                                             (soluble)  Aminogram                                                ______________________________________                                        Ile         7.6          6.8                                                  Leu         8.9          8.2                                                  Hys         8.7          8.8                                                  Met         1.6          1.6                                                  Cyst        3.7          2.4                                                  Phe         2.8          3.1                                                  Tyr         3.3          3.3                                                  Thr         7.8          7.0                                                  Trp         3.4          3.3                                                  Val         5.3          5.8                                                  Ars         1.1          1.6                                                  His         1.7          1.9                                                  Ala         3            3.7                                                  Asp         11.5         11,2                                                 Glu         13.9         18,1                                                 Gly         2.0          2.3                                                  Pro         4.7          8.1                                                  Ser         5.0          4.7                                                  ______________________________________                                    

The product is moreover very soluble and has an agreeable sweet tastwhich is caused by the presence of the glycosyl CMP.

EXAMPLE 2

In this example a lactic whey was treated. The whey coming from lacticcoagulation has no CMP.

The coagulation of the milk was obtained by the addition of lactic acidup to a pH of 4.6. After removing the curd, the pH was adjusted to a pH6.6 by adding potassium hydroxide 2/1000 trisodium citrate was added toavoid the problems of clogging the membranes with calcium salts. Priorto ultrafiltration the acid whey was subjected to centrifugation at 1000g for 15 minutes.

Ultrafiltration was then carried out at 25° C. in a DC 10ultrafiltration module with XM 50 membranes (see Example 1). Thecompositions of the permeate and the retentate during ultrafiltrationare indicated in table 3.

The previously obtained ultrafiltrate was then again ultrafilteredacross an AM₂ membrane with a Romicon DC 10 module at 15° C. Thecompositions of the retentate and the permeate are recorded in table 4.

The retentate of the second ultrafiltration which constitutes the soughtproduct therefore has the following approximate composition by weight:

    ______________________________________                                        lactoglobulin     37%                                                         α-lactalbumin                                                                             56%                                                         1% soluble nitrogen                                                                              7%                                                         ______________________________________                                    

Ultrafiltration through a gel performed in the same conditions as inExample 1 but in a column one meter high containing G 75 gel clearlyshows the peak 1 corresponding to the α-lactalbumin and peak 2corresponding to β-lactoglobulin. FIG. 3 of the accompanying drawingscorresponds to this case.

The theoretical aminogram of this protein solution would be:

    ______________________________________                                        Ile      6.4           Val    4.9                                             Leu      12.2          Arg    1.7                                             Lys      10.2          His    2.2                                             Met      1.7           Ala    3.8                                             Cys      4.8           Asp    14.7                                            Phe      3.8           Glu    14.4                                            Tyr      4.4           Gly    23                                              Thr      4.9           Pro    2.7                                             Trp      4.4           Ser    4.2                                             ______________________________________                                    

EXAMPLE 3

This example concerns the preparation of milk having the composition ofmother's milk. A product which satisfies this requirement has thefollowing composition:

    ______________________________________                                        Proteins            1.65       g                                              of which 0.82 g of the product                                                of example 1 or 2 above                                                       of which 0.83 g of total milk                                                 proteins                                                                      Lipids              3.5        g                                              of which vegetable oil rich in                                                polyunsaturated acids or fatty                                                acids : 1 g                                                                   Glucides:           7.5        g                                              lactose                                                                       Vitamins                                                                      A,E,B.sub.1, B.sub.2, B.sub.6, B.sub.12, PP, Calcium                                              according to the re-                                      penthotenate, folic acid, vitamin                                                                 commandations of                                          C, biotine, K       ESPGAN* Committee on                                                          Nutrition "Guidelines on                                                      Infant Nutrition", 1976                                   Nutrition                                                                     Minerals            according to the recom-                                   iron, sodium, calcium, potassium,                                                                 mandation of ESPGAN                                       magnesium, mangenese, phosphorous                                                                 Committee on Nutrition                                    chlorine, copper, zinc.                                                                           "Guidelines on Infant                                                         Nutrition", 1974                                          ______________________________________                                         *European Society for Pediatric Gastroenterology and Nutrition.          

EXAMPLE 4

This example is concerned with an intensive-care product enterallyadministered to patients requiring a protein intake of the order of 7 to12% of the Total Caloric Intake. Such a product satisfies nutritionalrequirements in case of mucoviscidosis or cystic fibrosis of thepancreas, kidney disorders as well as patients suffering from aninfection or inflammation of the intestinal wall. These proteins arepreferably supplied in pre-digested form.

A suitable centesimal composition is the following:

    ______________________________________                                        Proteins            2.50       g                                              of which 50% total milk proteins                                              50% of the product of the                                                     invention                                                                     Lipids                                                                        a mixture of equal parts of:                                                  butter oil   0.5   g                                                          T.C.M.       0.5   g                                                          corn oil     0.5   g                                                          sunflower oil                                                                              0.5   g          4.10     g                                      glycerol mono-                                                                             2.1   g                                                          stearate                                                                      Glucides                                                                      glucose polymers                                                                           10    g                                                          glucose      1.5   g          13.00    g                                      galactose    1.5   g                                                          Vitamins                                                                      A,D,E,B.sub.1, B.sub.2, PP, B.sub.5                                                                   according to the                                      B.sub.6, B.sub.12, folic acid                                                                         recommendations                                       biotine, vit. C         of FAO/WHO                                            Minerals            0.455      g                                              calcium, sodium, potassium                                                    magnesium, phosphorus, zinc                                                   iron,copper, manganese,                                                       chlorine, iodine                                                              Distilled water     q.s.p. 100                                                ______________________________________                                    

EXAMPLE 5

This example relates to an intensive-care product usable through theenteral tract of patients necessitating a protein intake of the order of23% of the total caloric intake in predigested form and a low lipidicintake. This may be the case with considerable tissue destruction afterserious traumas and burns.

An appropriate centesimal composition is the following:

    ______________________________________                                        Proteins          8           g                                               of which 50% meat proteins                                                    (trimmed and defatted beef)                                                   50% of the product according                                                  to the invention                                                              Lipids                                                                        T.C.M.    1.40   g                                                            oil very rich                                                                           1.40   g                                                            in essential                2.90      g                                       fatty acids                                                                   emulsifier                                                                              0.10   g                                                            Glucides                                                                      small glucose                                                                           12.7   g                                                            polymers                                                                      glucose   3      g          18.7      g                                       galactose 3      g                                                            Vitamins                                                                      A,D,E,B.sub.1, B.sub.2, PP, B.sub.5, B.sub.6, B.sub.12,                                         according to FAO/WHO                                        folic acid, biotine,                                                                            recommandations                                             vitamin C                                                                     Minerals                                                                      calcium, sodium, potassium, phos-                                                               0.455       g                                               phorus, zinc, iron, copper,                                                   manganese, chlorine, iodine                                                   Distilled water   q.s.p 100                                                   ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        RENTEN-                                                                       TATE         PERMEATE                                                         N.sub.T NPN.sub.12%                       NPN.sub.12% /                       g/l     ppm      N.sub.T                                                                             NPN.sub.12%                                                                          NPN.sub.2%                                                                           ES   N.sub.T                             ______________________________________                                        0    7.7    52.8                                                              1                    2.0 294    220    58.1 70.2                              2                        224                                                  3    16.3            2.7 249                59.0                              4                        242                                                  5    23.6            3.2 241    326         48.3                              6                        243                                                  7                        245                50                                8    24.8            3.1 247    333                                           9                        254                52.7                              10   25.8                256                                                  fin. 21.2                262    314                                           ret.                                                                          Average, permeate                                                                          3.1   249      305    63.9                                       Starting with the values TCA.sub.2% and TCA.sub.12% the average               composition of the permeate is as follows:                                    N 450 ppm breaking                                                                          60 ppm   β-lactoglobulin                                                                       13.3%                                     down into:   250 ppm   soluble N    55%                                                    140 ppm   α-lactalbumin                                                                        31%                                       ______________________________________                                    

                                      TABLE 4                                     __________________________________________________________________________    RETENTATE                 PERMEATE                                                    NPN.sub.2%                                                                         NPN.sub.12%     NPN.sub.12                                       N.sub.T g/l                                                                           ppm  ppm  ES g/l                                                                            N.sub.T /ES                                                                       N  ppm NPN/N                                                                              N/ES                                    __________________________________________________________________________    0   3.1 305  249  63.9                                                                              4.8                                                     1                         1.40                                                                             198.4                                                                              88  2.7                                     2   4.5                                                                       3   5.5      265  69.6                                                                              7.8 1.80                                                4   6.8                                                                       5   9.1      269  73.8                                                                              12.4                                                                              1.9                                                 6   9.7                                                                       7   12.4       203.1                                                                            54.3                                                                              22.9                                                                              1.4                                                 8   12.2                                                                      9   12.8                                                                              873  121  32.1                                                                              39.8                                                                              0.61                                                                             96  100  2.7                                     .sup.≠ Ret.                                                                 15.9     132  35.3                                                                              45                                                      __________________________________________________________________________     .sup.≠ Final retentate after concentration                         

What we claim is:
 1. A process for obtaining an alpha-lactalbumin enriched product from sweet whey, comprising:(a) adjusting the pH of the whey to about 6.6, whereby a pH-adjusted whey is obtained; (b) subjecting the pH-adjusted whey to a first ultrafiltration at a temperature in the range of 45°-60° C. on a membrane having a molecular weight cut-off adopted to retain soluble proteins, whereby a first ultrafiltrate is obtained; (c) separating the first ultrafiltrate; (d) subjecting the first ultrafiltrate to a second filtration on a membrane having a molecular weight cut-off adapted to retain alpha-lactalbumin and whereby a retentate is formed; and (e) collecting the retentate.
 2. The process of claim 1, wherein the milk used is skim milk.
 3. The process of claim 1, wherein the sweet whey is obtained from cooked or uncooked pressed curds.
 4. The process of claim 1, wherein the sweet whey is obtained from fresh curds.
 5. The process of claim 1, wherein the cut-off of the membranes of the first ultrafiltration step is generally greater than about 5,000.
 6. The process of claim 5, wherein the cut-off of the membrane of the second ultrafiltration step is less than about 5,000.
 7. The process of claim 6, wherein the cut-off of the membrane of the second ultrafiltration is between about 1,5000 and 2,000.
 8. The process of claim 1, wherein the whey is used in the first ultrafiltration step prior to any heat treatment.
 9. The process of claim 1, wherein the whey is used in the first ultrafiltration step without undergoing pasteurization.
 10. The process of claim 1, wherein said pH adjustment step comprises adding a basic reagent.
 11. The process according to claim 10, wherein the basic reagent is a compound selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, calcium hydroxyde and ammonium hydroxide.
 12. The process of claim 11, wherein the basic reagent comprises potassium hydroxide.
 13. The process of claim 1, comprising carrying out the second ultrafiltration step at about ambient or slightly lower temperature.
 14. The process of claim 1, comprising carrying out the second ultrafiltration step at a temperature of the order of about 15° C.
 15. The process of claim 13, wherein the second ultrafiltration is a diafiltration comprising adding to the ultrafiltrate of the first ultrafiltration step pure water upstream of the ultrafiltration membrane for the second ultrafiltration.
 16. The process of claim 13, wherein the second ultrafiltration is a diafiltration comprising adding to the ultrafiltrate of the first ultrafiltration step an aqueous solution containing mineral salts upstream of the ultrafiltration membrane for the second ultrafiltration. 